Physiological Response Of Powdery Mildew Of Populus Davidiana×P.bolleana To Host Interactions And Genome Sequencing And Analysis Of Powdery Mildew Of Populus Davidiana×P.bolleana

Powdery mildew is an important plant specific parasitic fungus,which generally occurs in fruit and vegetable crops,ornamental plants and economic trees.At present,there are few reports on powdery mildew occurring on poplar.In this experiment,powdery mildew of Populus davidii was studied by observing the formation process of conidia,germ tube and appressorium;Measuring the physiological response of the host plant during its infection plays an important role in preventing and controlling the occurrence of diseases.At the same time,based on the whole genome sequencing and preliminary analysis,the secretory proteins and effector proteins in the genome were predicted and analyzed.It is helpful to understand pathogens in essence and provide high-quality DNA data for molecular operation in the future;To clarify the direction for revealing the pathogenic mechanism of powdery mildew of Populus davidii;It lays a foundation for screening new disease resistance genes of host.The main results are as follows:1.The morphology and germination characteristics of conidia of powdery mildew of Populus davidii were observed and further revealed.The results showed that the size of conidia was 32 ～ 45 × 10～16 μ m.It is long oval,colorless and transparent.Most are solitary and a few are arranged in chains.The germination was hardly affected by the contact medium,but the germination time and germ tube length were slightly different in hydrophilic and hydrophobic media.In addition,conidia can germinate in water and glucose solution to form germ tube and lobed appressorium,and glucose solution can significantly promote the germination rate of spores.2.The physiological responses of tissue cultured seedlings of Populus davidii to powdery mildew infection were systematically measured.The results showed that the activities of SOD,pod and cat increased significantly at first and then decreased slowly with different infection periods;As a product of membrane peroxidation,MDA shows a rising trend.3.The genome of powdery mildew of Populus davidii was sequenced and analyzed.The sequencing results showed that the genome size of the sample was 43.15 mb,and a total of5861 genes were predicted after annotation.The predicted genes were enriched and analyzed through go,KOG and KEGG databases.There were 3337 GO annotation genes,of which 11 genes related to spore germination and spore formation were screened,and 7 genes directly related to host infection;There are 4338 eggnog annotated genes,of which 611(14.08%)are closely related to the life and metabolism pathway of fungi,323(5.51%)are involved in posttranslational modification,turnover and molecular chaperone,and 262(4.47%)are related to intracellular transport,secretion and vesicle transport;A total of 2544 genes related to 360 KEGG pathways were obtained from KEGG annotation,including 1033 genes related to metabolic pathway;The number of genes involved in genetic information processing pathway was up to 1948;441 signal transduction pathway related genes.4.The secretory proteins in powdery mildew of Populus davidii were predicted and analyzed.A total of 137 secretory proteins were predicted,and the length was concentrated in100 ～ 500 AA;The amino acid composition of signal peptide cleavage sites-3 and-1 is a-x-a type;In the secretory proteome,81 functions were annotated,mainly involving protein posttranslational modification and molecular chaperone,carbohydrate transport and metabolism,etc;In addition,17 cazymes were predicted,of which the GHS family accounted for the majority.Further predict the effector proteins in the secretory proteome of Populus tomentosa,and a total of 34 candidate effector proteins are predicted,of which 10 can be compared with the pathogenic effector proteins of other pathogens in the phi database.